Research On Molecular Characteristics And Drug Resistance Of CA-MRSA Isolated From Children In Tangshan

Objectives To investigate the characteristics,molecular typing and drug resistance of clinical infection by CA-MRSA among children in Tangshan.Methods Collected strains of S.aureus from infected children between Aug 2013 and Dec2016.Tested and analyzed by BD Phoenix?-100 Automated Microbiology System.Using disc diffusion method of Cefoxiti obtained MRSA.and case investigation revealed that they were CA-MRSA.mec A gene was detected to confirmed MRSA by simple PCR and agarose gel electrophoresis.SCCmec typing was conducted by multiplex PCR and agarose gel electrophoresis.Further conduct pvl,spa and MLST typing by simple PCR,Agarose gel electrophoresis and DNA sequencing.Results 1 102 strains of CA-MRSA were confirmed by conforming case standard.the major samples were sputum and pus.Total of 64 patients were male and others were female,Ages ranged from 0 to 14 years old.Patients of 0-28 days old accounted for 23.5%.Patients of 28 days to 6 months old accounted for 44.1%.Patients of 6 months to 1 years old accounted for 14.7%.Patients of 1-3 years old accounted for 13.7%.Patients of 3-14 years old accounted for 3.9%.2 Pneumonia(55,53.9%)was the most common infection.A total of 37 patients had skin soft tissue infection,and a total of 8 patients had bloodstream infection.3 102 strains were sensitive to Linezolid,Teicoplanin,Vancomycin,and were resistant to ?-lactams antibiotic.and the percentage of the 102 strains resistant to Erythromycin,Clindamycin,Trimethoprim,Tetracycline and Tobramycin were 93.1%,89.2%,44.1%,26.5% and 13.7% respectively.These were superior than others.The rest of the strains had different drug resistance.4 Five SCCmec typings were observed,the most common type was SCCmec IV(54.9%,56/102),followed by SCCmec V(18.6%,19/102),SCCmec III(11.8%,12/102),SCCmec II(3.9%,4/102)and SCCmec I(1.0%,1/102).The prevalence of pvl postive was 29.4%(30/102).There were 17 spa typings among which the most common was t437(52.0%).the other spa typings found were t324,t441,t021,t309,t318,t668,t968,t1751,t3523,t3527,t3424,t2592,t127,t037,t030,t311.3 strains with genotypes were unknown.14 distinct sequence types(STs)were identified among the 102 isolates,the most prevalent was ST59,followed by ST910(10)and ST88(13).the other sequence types found were ST5,ST398,ST30,ST1777,ST82,ST45,ST338,ST1,ST72,ST239 and ST22.5 Being the most prevalent clone,MRSA-ST59-SCCmec IVa with t437 accounted for 29.4%.It was followed by MRSA-ST59-SCCmec V with t437(9.8%)among the 102 isolates.Strains of MRSA-ST59-SCCmec IVa with t437 were sensitive to Linezolid,Teicoplanin,Vancomycin,and were resistant to ?-lactams antibiotic,and the strains resistance to Erythromycin,Clindamycin,Trimethoprim and Tetracycline were90.0%,83.3%,63.3% and 36.7% respectively.These were superior than others.The rest of the strains had different drug resistance.Conclusions 1 Pneumonia and skin soft tissue infection were the most common infection.The most common patient group was infants,whose infection was caused by CA-MRSA.2In empiric treatment Erythromycin and Clindamycin should be used with care.Linezolid,Teicoplanin,and Vancomycin were alternated to cure patients,the better method was drug combination from children themselves with infection caused by CA-MRSA.3 The mostcommon bacterial clone was MRSA-ST59-SCCmec IVa with t437 from children with infection caused by CA-MRSA,similar to the other parts in mainland Chuna.4 Strains of MRSA-ST59-SCCmec IVa with t437 were sensitive to Linezolid,Teicoplanin,Vancomycin,resistant to ?-lactams antibiotic,and more resistant to Erythromycin,Clindamycin,Trimethoprim and Tetracycline than others.